There
is a growing interest in using e-learning for geometry and / or technical
drawing teaching both in distance education and as a supplement to in-class
courses. Although there are many geometry drawing programs being used for
educational purposes, some shortcomings may be identified in their user
interfaces when used as a (partial) replacement for paper and pencil practice.

Most
of those programs adopt a conventional Graphic User Interface (GUI), based on
windows, icons, menus and pointing (WIMP). Due to this, like any other
software, they demand some user’s time to be mastered. Likewise, most of
them have many features, allowing a full range of graphical constructions (tangent,
parallel and perpendicular lines, middle point, bisectors, inscribed and
circumscribed circles etc.) to be executed with a few clicks. Finally, their
GUIs are very abstract, far apart from the drawing instruments the students
use in classroom.

A
non-intuitive GUI is a particular problem in that context because, among other
reasons, as it is widely known, the credits assigned to graphics disciplines,
with a few exceptions, have been reduced worldwide. Hence, it is very
undesirable to have a student spending time to learn how to drive a new
program instead of practicing the target topics of a course in the short time
available. Furthermore, as this kind of software usually covers only a small
part of a discipline contents its use is occasional and is not worth investing
much time for learning it.

Different
from a CAD system, where drawing efficiency is among the most important
requirements, an educational tool must sacrifice execution speed in favor of
pedagogic issues, if needed. Therefore, a plethora of features for easy
execution of any foreseeable construction is not only undesirable because it
precludes the student of performing a geometrical construction the way he must
practice, but also makes steeper the software learning curve.

Concerning
the abstraction aspect of the GUI, we are not sure to which extent the use of
an artificial, computer interface for drawing can hamper the abilities of an
apprentice regarding the correct manipulation of drawing instruments (compass,
triangles, ruler, pencil). We plan to investigate this issue.

Therefore,
we conclude that an educational geometry drawing software GUI should be
intuitive and concrete. This paper describes an interface based on a real
world metaphor featuring a compass, a 45° triangle, a 30°/60° triangle, a
pencil and an eraser. This interface is under development by the authors and
will integrate an online dynamic geometry educational software.

The
virtual instruments in the proposed interface closely emulate their real
counterparts (both visually and behaviorally) and it is hoped that their
manipulation will be intuitive enough to dispense any explanation or
instruction. Towards this goal, a major issue is the fact that the interaction
in the proposed interface is one-handed (select/drag with the mouse) while the
user utilizes both hands when interacting with the drawing instruments in the
real world. Some clever techniques were employed to circumvent this problem
and, at the same time, keep the interaction intuitive.